A touch screen provides a man-machine interaction mode, which is currently the simplest, most convenient and most natural interaction mode. The touch screen is widely used in information inquiry, industrial control, self-service, multimedia teaching, electronic games, etc. In particular, due to the fact that a larger visual area (or an operable area) can be provided, the large size (20 inches or larger) touch screen has come into more widespread use.
Among various touch screen types, the capacitive touch screen is one of large size touch screens, and has a better application prospect due to accuracy, usability, abrasion resistance, long service life, etc. An example of a large sized capacitive touch screen is shown in FIGS. 1-3. The touch screen includes an outer screen 1 and an inner screen 2 (see FIG. 2), which are connected via a bonding element 4 (e.g. a double-faced adhesive tape, an adhesive, etc.). The outer screen 1 is used for touch control, and the inner screen 2 is used for display. In the present example, the outer screen 1 is of a single-piece structure, and only includes a touch control layer.
A sensing unit array and a driving unit array (collectively referred to as 13) are provided on a touch control layer of the outer screen 1 having a single-piece structure in a single-sided arrangement. The sensing unit array and the driving unit array are arranged on a same surface of the outer screen 1 (in FIG. 1, the surface is the front surface of the outer screen 1, which is represented by the front surface of the drawing sheet). Specifically, in the example shown in FIG. 1, the sensing unit array is arranged on the front surface of the outer screen 1 and is particularly arranged in the visible region 12 of the outer screen 1. The sensing unit array is formed by arranging a plurality of rows of sensing units which are connected in series. Two ends of each row of sensing units are respectively connected to sensing electrodes 13a and 13b arranged at a lower edge of the outer screen 1, through an electrode wire (usually made of a silver paste material). The driving unit array is also arranged on the front surface of the outer screen 1, and particularly arranged in the visible area 12 of the outer screen 1. The driving unit array is formed by arranging a plurality of columns of driving units which are connected in series. As to two ends of each column of driving units, the upper end is suspended, while the lower end is connected to a driving electrode 13c arranged at the lower edge of the outer screen 1, through an electrode wire (usually made of the silver paste material). The electrode wires, the sensing electrodes and the driving electrodes are all arranged within the non-visible region 11 of the outer screen 1. A plurality of sensing electrodes 13a are electrically connected to an FPC (flexible printed circuit) 31 which is fixed at the lower edge of the outer screen 1 (the sensing electrodes 13b are similarly electrically connected to another FPC). A plurality of driving electrodes 13c are electrically connected to the FPC 32.
Another example of a large size capacitive touch screen is shown in FIGS. 4-6. The touch screen includes an outer screen 1 and an inner screen 2, which are connected to each other through a bonding element 4 (see FIG. 5). Wherein the bonding element 4 and the inner screen 2 are the same as those of the previous example. The outer screen 1 is of a fully-attached structure, and the outer screen 1 includes a touch control layer 10 and a protection layer (such as a glass plate) 20. The protective layer 20 is fully attached to the touch control layer 10 to form an outer screen 1 having a fully-attached structure, as shown in FIG. 6. The touch control layer of the outer screen 1 having a fully-attached structure adopts two-sided arrangement. The sensing unit array and the driving unit array are respectively arranged on two surfaces of the outer screen 1 (in FIG. 4, the two surfaces are the front surface and the back surface of the outer screen 1, and the front surface and the back surface of the outer screen 1 are respectively represented by the front surface and the back surface of the drawing sheet; units depicted with the dotted lines in FIG. 4 are the ones arranged on the back surface). Specifically, in the example shown in FIG. 4, the sensing unit array is arranged on the front surface of the outer screen 1, while the driving unit array is arranged on the back surface of the outer screen 1. Except for the difference that the sensing unit array and the driving unit array are respectively arranged on the two surfaces of the outer screen 1, the outer screen 1 in the present example is the same as that of the previous example.
A large size (more than 20 inches) capacitive touch screen has many rows of sensing units and many columns of driving units, and thus there are a lot of electrode wires connecting these rows of sensing units and columns of driving units. These electrode wires occupy most of the non-visible region 11 of the outer screen 1. Therefore, in the prior art, when the outer screen 1 and the inner screen 2 are connected, the bonding element 4 is inevitably applied on the electrode wires in the non-visible region 11 of the outer screen 1, as shown in FIGS. 2 and 5. The electrode wires are generally made of a silver paste material. The adhesion force between these electrode wires and the surface of the outer screen 1 is not strong enough, so that the inner screen 2 and the outer screen 1 cannot be effectively connected. Particularly, when the large size touch screen needs to be vertically placed for a long time period (as shown in FIGS. 3 and 6), if no extra device for supporting the inner screen 2 and the outer screen 1 is provided, the weight of the inner screen 2 and the outer screen 1 applies a tearing force on the electrode wires, wherein the tearing force is parallel to the surface of the outer screen 1. Thus, the electrode wires are likely to shift and even fall off from the surface of the outer screen 1, which makes the touch screen inoperable. Furthermore, as to the outer screen 1 of the fully-attached structure shown in FIGS. 4-6, due to the fact that a large area of the non-visible region 11 accommodating a large number of electrode wires is needed, the area of the touch control layer 10 also needs to be large. It is unlikely to use a protection layer 20 having a larger area which can make the inner screen 2 fixed to the protective layer 20 through the bonding element 4. Therefore, the bonding element 4 needs to be at least partially applied on the electrode wires in the non-visible region 11 of the touch control layer 20.
Therefore, to solve the above problems, a person of ordinary skill in the art is dedicated to developing a large size capacitive touch screen, a method of connecting the inner screen to the outer screen, and a connector.